The present invention relates to a scroll-type fluid machine for transporting and boosting gases or liquids and, more particularly, to a small-sized scroll-type fluid machine which is suitable for handling a fluid having very small flow rate.
As known to those skilled in the art, a scroll-type fluid machine has an orbiting scroll member including an end plate and a spiral wrap axially projecting from the end plate, and a stationary scroll member having a construction similar to the construction of the orbiting scroll member. These scroll members are assembled together such that their wraps mesh with each other. The orbiting scroll member is driven so as to make an orbiting motion around the axis of the stationary scroll member without rotating on its own axis.
In known scroll-type fluid machines, a rotation prevention member such as an Oldham's coupling is disposed between the orbiting scroll member and the stationary scroll member, as disclosed in the specifications of U.S. Pat. Nos. 4,522,575 and 4,552,518. The orbiting motion of the orbiting scroll member is effected by a crankshaft having an eccentric pin which engages with the orbiting scroll member. As the crankshaft is driven by a motor, the orbiting scroll member engaging with the crank pin orbits around the axis of the stationary scroll member without rotating on its own axis. In consequence, chambers varying in volume are formed among the wraps and the end plates of both scroll members so as to suck and compress the fluid, thereby transporting or boosing the fluid.
Since, in the known scroll-type fluid machine, a rotation prevention member such as an Oldham's coupling for preventing the orbiting scroll member from rotating on its own axis, a crankshaft for converting the rotational motion of a motor to the orbiting motion of the orbiting scroll member and the electric motor having a large volume and a heavy weight for producing the required driving power are used, it is difficult for the known machine to have a small size and a light weight. In addition, an oil-free construction can hardly be provided in the known machine because of the necessity for lubrication of the bearings which rotatably support the crankshaft. Furthermore, electromagnetic sounds generated by the electric motor causes high levels of vibration and noise.
Hitherto, discussions have been done in regard to the driving of the orbiting scroll member, and various improved arrangements have been proposed which can support the orbiting scroll member stably during driving. In most cases, the orbiting motion of the orbiting scroll member is made by a crankshaft which engages with a central portion of the orbiting scroll member, so that the orbiting scroll member receives a moment of force due to centrifugal force, pressure of the gas and the crankshaft. The moment of force applied to the orbiting scroll member causes fluttering motion of the orbiting scroll member during the orbiting motion. Since the outer peripheral portion of the orbiting scroll member flutters within a very small clearance defined by the frame of the machine and the outer peripheral portions of the stationary scroll member and the orbiting scroll member, vibration and noise are generated by the outer peripheral portion of the orbiting scroll member contacting with the adjacent portions of the frame and the stationary scroll member.